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HUBS192 EXAM > GI System > Flashcards

GI System Flashcards

1
Q

Main component involved in mechanical digestion?

A

Motility

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2
Q

Main component involved in chemical digestion?

A

Secretion of fluid and enzymes

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3
Q

How does the nervous system regulate/control digestion?

  • ENS
  • CNS
A

ENS: primary neural system controlling GI function
CNS: modulates activity of ENS

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4
Q

What does the parietal peritoneum line?

A

the abdominal + pelvic cavities (peritoneal cavity)

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5
Q

What does the visceral peritoneum cover?

A

The external surfaces of most abdominal organs

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6
Q

What is mesentery?

A

Double layer of peritoneal membrane connecting organ to body wall

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7
Q
  • Structure of the peritoneal membrane

- What does it secrete?

A
  • Simple squamous epithelium

- Secretes serous fluid

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8
Q

parietal and visceral peritoneum

A

Single layer of peritoneal membrane

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9
Q

Omentum

A

Double layer of peritoneal membrane connecting organ to organ

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10
Q

Momentum and mesentery store what?

A

Fat

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11
Q

Arterial supply to abdominal viscera:

  • Which arteries branch off the abdominal aorta?
  • Where does this supply blood in a foetus?
A
  1. Celiac trunk (foregut)
  2. Superior mesenteric (midgut)
  3. Inferior mesenteric (hindgut)
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12
Q

Arterial supply to abdominal viscera:

  • Branches of the celiac trunk and which organs they supply
A
  1. Common hepatic
    - Liver
    - Duodenum
    - Pyloric stomach
    - Pancreas
  2. Left gastric
    - Lower oesophagus
    - Stomach
    - Liver
  3. Splenic
    - Spleen
    - Pancreas
    - Stomach
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13
Q

Arterial supply to abdominal viscera:

  • Branches of the superior mesenteric and which organs they supply
A
  1. Intestinal arteries
    - lieum
    - jejunum
  2. Ileocolic artery
    - ileum
    - cecum
    - appendix
  3. Colic arteries
    - ascending colon
    - Transverse colon
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14
Q

Arterial supply to abdominal viscera:

  • Branches of the inferior mesenteric and which organs they supply
A
  1. Left colic artery
    - Descending colon
  2. Sigmoid arteries
    - sigmoid colon
  3. superior rectal artery
    - rectum
    - anal canal
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15
Q

Characteristic of blood drained via hepatic portal circulation

A

nutrient rich

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16
Q

Composition of GI tube wall: mucosa

- What does it contain

A
  1. Epithelium (mucous secreting)
  2. Basement membrane
  3. Lamina propria (LFCT)
    - Gland ducts
    - Nerve fibres
    - BVs and lymph vessels
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17
Q

Composition of GI tube wall: submucosa

- What does it contain?

A
  • FCT
  • blood + lymph vessels
  • glands
  • meissner’s/submucosal plexus
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18
Q

Composition of GI tube wall: muscularis

A

Smooth muscle:

  • inner circular
  • outer longitudinal
  • myenteric plexus (b/w layers)
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19
Q

Composition of GI tube wall: adventitia

A

FCT

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20
Q

Which parts of the GI tract are lined w/ stratified squamous epithelium?
- purpose?

A

Mouth
Oesophagus
Anal canal
- protection

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21
Q

What epithelial tissue lines the SI

A

Simple columnar

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22
Q

What is the muscle transition in the oesophagus

A

skeletal to smooth

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23
Q

What epithelial tissue lines the stomach?

- Which cells line the gastric glands? What do they secrete?

A
  • Simple columnar
    Gastric glands:
  • Mucous cell; secretes mucous
  • Chief cell; secretes pepsinogen
  • Parietal cell; secretes HCl + intrinsic factor
  • Endocrine cell; secretes hormones (gastrin and ghrelin)
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24
Q

Epithelial tissue lining the LI?

A

Simple columnar

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25
Q

Composition of the smooth muscle in the intestines?

A
  • inner circular

- outer longitudinal

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26
Q

Which type of digestion occurs in the mouth?

A

Mechanical

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27
Q

Parotid salivary glands:

  • Secrete?
  • Relative size?
  • Located?
  • Secrete what % of total saliva
A
  • Serous fluid only
  • Largest salivary glands
  • Inferior and anterior to the ear
  • 25-30% of total saliva
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28
Q

Submandibular salivary glands

  • Secrete?
  • Location of submandibular duct
  • Secrete what % of total saliva
A
  • Secrete mixed serous and mucous
  • submandibular duct opens through papilla in the floor of the mouth
  • 60-70% of total saliva
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29
Q

Sublingual salivary glands

  • Secrete?
  • Located?
  • Secrete what % of total saliva
A
  • Mucous
  • Multiply, tiny ducts open onto the anterior surface of the oral cavity
  • 3-5% of total saliva
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30
Q

Functions of saliva

A
  • Moistens ingested material –> bolus
  • Moistens, cleanses and lubricates oral cavity
  • Begins chemical digestion of carbohydrates (amylase)
  • Antibacterial action (lysosomes)
  • Dissolves food –> taste
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31
Q

Epithelium of the oropharynx

- purpose

A

Stratified squamous

- protection

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32
Q

Oesophagus:

  • layers?
  • composition of layers?
  • What is b/w the oesophagus and the stomach? Made up of?
A

Layers

  1. Mucosa
    - stratified squamous epithelium
  2. Submucosa
    - mucous glands
  3. Muscularis
    - Skeletal to smooth muscle
  4. Adventitia

Lower oesophageal sphincter
- ring of thickened smooth muscle

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33
Q

Stomach:

  • 3 sections?
  • epithelium
  • muscularis layers (inner to outer)
  • Folds: name, made up of, allows for?
  • Sphincter?
A
  • Fundus, body, pylorus
  • Simple columnar
  • oblique, circular, longitudinal
  • rugae; mucosa and submucosa; expansion
  • Pyloric sphincter
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34
Q

Characteristics of chief cells

A
  • Rough ER

- Granules

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35
Q

Characteristics of parietal cells

A
  • Lots of mitochondria
  • Large SA
  • Highly folded (microvilli)
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36
Q

Function of gastrin

A
  • stimulates digestive function

- acts on PC to stimulate HCl secretion

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37
Q

Function of ghrelin

A
  • Stimulates appetite
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38
Q

3 functions of omenta

A
  1. Fat deposition
  2. Immune contribution
  3. Infection and wound isolation
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39
Q

What does the greater momentum attach?

A

Stomach to the transverse colon

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40
Q

Location and function of pyloric sphincter

A
  • B/w stomach + SI

- Controls the release of chyme into the duodenum

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41
Q

What + where are the specialised cells in the duodenum + their purpose
- Other function?

A
  1. Mucous secreting cells in the epithelium: protection from acid
  2. Alkaline mucous secreting glands in submucosa: protection from acid
  3. Neutralise pH by stimulating secretion of bicarbonate
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42
Q

What are the layers of the SI wall + any structures w/in them

A
  1. Mucosa: vili w/ microvilli
  2. Submucosa: plicae circulares
  3. Muscularis: inner circular and outer longitudinal
  4. Adventitia
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43
Q

What is glycocalyx?

A

A glycoprotein coat on the microvilli which holds brush border enzymes for contact digestion.

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44
Q

What is segmentation?

A

Localised contractions of circular muscle; moves contents back + forth —> mixes food w/ digestive juices + facilitates absorption

45
Q

What does the submucosal plexus regulate?

A

Secretion

46
Q

What does the myenteric plexus regulate?

A

Motility

47
Q

Function of bile salts

A

Emulsify lipids

48
Q

What does the pancreas produce?

A

Digestive enzymes + bicarbonate

49
Q

What is the sphincter associated with the hepatopancreatic duct?

A

Sphincter of Oddi

50
Q

What is the duct formed by the union of the pancreatic duct + the common bile duct? Leads into?

A

Hepatopancreatic duct

- duodenum

51
Q

What anchors the transverse colon to the body wall?

A

Transverse mesocolon

52
Q

Sections of the LI

A

Cecum –> ascending colon –> hepatic flexure –> transverse flexure –> splenic flexure –> descending colon –> sigmoid colon –> rectum –> anal canal

53
Q

What is the sphincter/valve between the ileum and the sphincter?

A

ileo-caecal valve

54
Q

What folds are associated w/ the LI?

A

Semilunar folds

55
Q

What are haustra?

A

Sacs formed in the LI when taeniae coli are contracted

56
Q

What are taeniae coli?

A

The outer longitudinal muscle layer of the LI arranged into tape-like strips

57
Q

What are epiploicae appendices?

A

Small pouches of the peritoneum filled with fat and situated along the colon

58
Q

Layers of the LI

A
  1. Mucosa; contains deep mucosal invaginations (crypts) and goblet cells
  2. Submucosa
  3. Muscularis
  4. Adventitia
59
Q

State of sphincter muscles during the 3 stages of defecation

A
  1. Rectum minimal stretch/pressure: internal contracted, external relaxed
  2. Rectum stretched: internal relaxed, external contracted
  3. Conscious defecation: both relaxed
60
Q

What does the liver portal triad consist of? What do they transport?

A
  1. Hepatic artery: oxygenated blood in from aorta
  2. Hepatic portal vein: deoxygenated, nutrient-rich blood in from digestive organs
  3. Bile duct: bile out from liver to gallbladder
61
Q

What is the basis of spontaneous activity in the GI tract

A

Basal Electrical Rhythm (BER):

  1. Spontaneous variations in membrane potential
  2. Produce action potentials (when threshold reached)
  3. Contractions
62
Q

What is the fasting motility pattern?

  • Time
  • activity
  • function
A
  • Migrating Motor Complex (MMC)
  • 4-5 hours after a meal, repeated approx. every 2h
  • 3 periods: inactivity, intermittent activity, intense activity
  • Function: house keeping (clears it out)
63
Q

What are the feeding motility patterns?

  • Where do they occur
  • Function
A
  1. Storage
    - Stomach
    - Distension
  2. Peristalsis
    - Oesophagus, stomach, SI, LI
    - Propulsion
  3. Segmentation
    - SI, LI
    - Mixing + exposure to absorptive surfaces
64
Q

How does storage occur in the stomach?

A
  1. Receptive relaxation:
    - increase in vol. w/out increase in pressure
    - Initiated by swallowing
  2. Relaxation of smooth muscle:
    - reduced thickness
65
Q

How does peristalsis facilitate the delivery of food?

- Activity over duration?

A
  • Peristaltic waves initiated on greater curvature
  • First hour: gentle activity; after 60-300 mins: more intense activity
  • Allows propulsion and retropulsion
66
Q

How much saliva do we produce per day?

A

1.5L

67
Q

Composition of saliva and their functions

A
  1. Mucus
    - Lubrication
  2. NaHCO3/NaCl
    - Dilution + optimum pH
  3. Enzymes (Amylase, lipase)
    - digestion
68
Q

Which component of the CNS regulates saliva?

A
  • Autonomic NS
69
Q

Vol. of gastric secretions per day? Mainly composed of?

A

2-3L

70
Q

What is the main gastric secretion when fasting?

A

Mucus

71
Q

Composition of gastric secretion when feeding? Functions?

A
  • NaCl
  • Acid: denatures proteins, pH, activates pepsinogen, protection
  • Mucus: protection
  • Bicarbonate
  • Pepsinogen (pepsin): digestion of proteins
  • Intrinsic factor: absorption of vitamin B12 (in SI)
72
Q

3 Phases of gastric secretion regulation

  • Function
  • Stimuli
  • Response
A
  1. Cephalic
    - Preparation for food
    - Stimuli = thought + chewing
    - Causes increased parasympathetic NS activity
  2. Gastric
    - Regulates secretion in stomach
    - Stimuli = distension + presence of AAs
    - Causes parasympathetic + ENS to stimulate PC + CC + gastrin production
  3. Intestinal
    - Controls amount of acid delivered to SI
    - Stimuli = food in duodenum/distension
    - PNS + ENS; Stimulates release of GIP, CCK and secretin; reduce gastric secretions
73
Q

Vol. of pancreatic secretion per day

A

1-1.5L

74
Q

Components of pancreatic secretion

- Secreted by?

A
  1. Enzymes (acinar cells)

2. Bicarbonate (ducts)

75
Q

Pancreatic secretion - enzymes

  • What are the types?
  • What do they target?
  • Secretion stimulated by?
A 
→ Lipolytic
- Lipase, phospholipase
- target lipids
→ Amylytic 
- amylase
- targets carbohydrates
→ Proteolytic 
- trypsin, chymotrypsin, carboxypeptidase
- targets proteins
→ Nucleolytic
- ribonuclease
- deoxyribonuclease
Stimulated by:
- Cholecystokinin (CCK)
76
Q

Pancreatic secretion - alkaline/HCO3 rich fluid

  • Produced by?
  • Function?
  • Stimulated by?
A
  • Duct cells produce isosmotic HCO3 rich solution
  • Neutralise chyme (acidic from stomach)
  • Creates optimum pH (for pancreatic & intestinal enzymes)
  • Stimulated by secretin
77
Q

Pancreatic secretion - CCK

  • What is it produced by?
  • Stimuli
  • What does it stimulate?
A
  • Produced by duodenal endocrine cells in response to digestive products in lumen (AAS, fats, carbohydrates)
  • Stimulates enzyme secretion (acinar cells)
78
Q

Pancreatic secretion - Secretin

  • Where is it produced?
  • Stimulus
  • What does it stimulate?
A
  • Produced by duodenal endocrine cells
  • in response to ↑ [H+] in lumen
  • Stimulates HCO3- secretion (duct cells)
79
Q

How much bile is secreted per day?

A

0.5L

80
Q

Composition of bile

A 
→ Bile salts + lecithin
- Fat digestion & absorption
→ HCO3 rich fluid
- Neutralizes acid chyme
→ Bile pigments
- Excretion
81
Q

Biliary secretion - Regulation

  • Where is bile produced and stored?
  • What stimulates release?
  • Where is bile delivered to?
  • What does bile contain?
  • What is its function?
A
  • Constantly produced by the liver and stored in gallbladder
  • Release stimulated by CCK
  • Delivered to SI
  • Contains cholesterol, waste products, alkaline fluid, bile salts and lecithin
  • Assists with lipid digestion
82
Q

Vol. of intestinal secretion per day

A

1.5L

83
Q

Intestinal secretions: SI + LI

A 
SI
- Mucus
- NaHCO3
LI
- mucus
84
Q

Carbohydrate digestion

A

Polysaccharide –> hydrolysis (salivary + pancreatic amylase) –> disaccharide –> hydrolysis (brush-border enzymes) –> monosaccharide

85
Q

Stages of lipid digestion

A
  1. Emulsification
    - Large droplets –> smaller droplets
    - Disperses them
    - Stomach + SI
  2. Stabilisation
    - Stops droplets from settling again
    - Bile salts
    - SI
  3. Hydrolysis
    - TAGs —> monoglycerides + fatty acids
    - Lipase + colipase
    - Lumen of SI
  4. Formation of micelles
    - Allows insoluble droplets to stay in water
    - Bile salts surround groups of ffas/monoglycerols
86
Q

Lipid digestion

A

Large fat droplet –> small droplets (emulsification) –> hydrolysis (lipase) –> fatty acids + monoglycerides + glycerol

87
Q

What are the factors affecting absorption?

A
  • Motility
  • Available surface area
  • Transport
  • Removal of substances from the interstitial space
88
Q

How does motility affect absorption?

A
  • Need correct rate of propulsion for digestion & absorption (otherwise abnormal bowel movement, i.e constipation, etc)
  • Exposure to absorptive surfaces
89
Q

How does SA affect absorption?

A
  • Rate of absorption proportional to SA

- Anatomical adaptions (villi, microvilli) maximise SA

90
Q

What are the 2 pathways for solute absorption?

A

Two pathways:
→ Paracellular pathway
- Solutes move b/w the cells, do not cross the cell membrane
- Relatively non-selective (can cross of small enough)
- Passive (requires a gradient)
- Only barrier is tight junctions b/w cells
→ Cellular pathway (selective)
- Solutes cross 2 cell membranes
- Insoluble substances need transport proteins

91
Q

Purpose of large blood flow in interstitial space?

A

Removes substances from interstitial space to maintain gradient (HOMG)

92
Q

Absorption of water

  • Process?
  • Gradient set up by?
A

→ Osmosis

- Gradient set up by absorption of salts & nutrients

93
Q

Absorption of Sodium (Na+)

  • Passive
  • Active
A

→ Passive movement via paracellular pathway
→ Active transport via the cells (requires transporters):
- Na+ transport alone
- Na+ absorption coupled to glucose or AAs

94
Q

Absorption of Carbohydrates

  • Passive
  • Active
A

→ Passive
- Monosaccharides
- Diffuse down gradients via paracellular pathway
→ Active
- Cotransport w/ Na+ across apical membrane via SGLT-1
- Crosses basolateral membrane via GLUT2
- Monosaccharides

95
Q

Absorption of Proteins

  • Passive
  • Active
A 
→ Passive
- Products of digestion (AAs)
- Diffuse down gradient via paracellular pathway
→ Active
- Cotransport w/ NA+
- AAs coupled to Na+
- Similar process to glucose
96
Q

Absorption of Fat

A

→ Products of digestion are lipid soluble

  • Can diffuse into cell
  • Delivered to brush border via micelles (fatty acids + monoglycerides)
  • In epithelial cell: Synthesised into triglycerides, packaged into chylomicrons which exit the cell via exocytosis + enter lacteals
97
Q

Absorption of Bile salt

  • Proportion reabsorbed?
  • Where does it occur?
  • Where does active transport occur?
  • Where does passive absorption occur?
A

→ Majority is reabsorbed

  • Occurs in distal portions of SI to promote fat absorption
  • Active transport in terminal ileum
  • Passive absorption in jejunum
98
Q

Absorption of Vitamins

  • Fat soluble
  • Water soluble
A

→ Fat soluble (ADEK): absorbed w/ fats
→ Water soluble
- Na+ dependent absorption (eg Vitamin C)
- Vitamin B12 (intrinsic factor)

99
Q 
Absorption of Vitamin B12
- What does it involve? 
Where is this secreted?
- How does it allow absorption?
- Active or passive absorption?
A

→ Involves intrinsic factor (secreted by stomach): binds to vitamin B12
→ Receptors in ileum bind IF/B12 complex
→ Vitamin B12 actively absorbed

100
Q

What regulates conditions in intestinal lumen?

A
  • vol.

- composition

101
Q 
Local reflexes (ENS)
- mediated by which receptors in GI mucosa? What do they detect/monitor?
A

1) Mechanoreceptors - Deistension
2) Chemoreceptors - Chemical composition of lumen
3) Osmoreceptors - Osmolarity

102
Q

Neural regulation - CNS role & components

  • Type of regulation?
  • Subdivisions and what they normally do
A

→ Extrinsic bidirectional regulation (sensory → effector)
→ 2 subdivisions of ANS
1) Parasympathetic NS
- In general stimulates motility & secretion
2) Sympathetic NS:
- In general inhibits motility & secretion

103
Q

Endocrine cells

  • Paracrine action
  • True endocrine action
A

→ Paracrine action
- Substance acts on cells in immediate vicinity of release
- Provides regional control in response to local conditions
→ True endocrine action
- Hormones released into circulation to target distant cells

104
Q

Gastrin:

  • Secreted by?
  • In response to?
  • Acts on?
  • Function?
A
  • Gastric cells in stomach
  • Gastric motility + secretions
  • Acts on parietal cells, gastric muscle
  • Stimulates secretion + motility
105
Q

GIP:

  • Secreted by?
  • In response to?
  • Acts on?
  • Function?
A
  • Small intestine
  • Fats in the SI
  • Acts on G cells/gastric muscle
  • Inhibits gastric secretion + motility
106
Q

Secretin:

  • Secreted by?
  • In response to?
  • Acts on?
  • Function?
A
  • Duodenum
  • Food/acid moving into duodenum
  • Parietal cells + pancreatic duct cells
  • Stimulates bicarbonate secretion + inhibits effects of gastrin (H+ secretion from PCs)
107
Q

CCK:

  • Secreted by?
  • In response to?
  • Acts on?
  • Function?
A
  • SI
  • Products of digestion entering duodenum
  • Pancreatic duct cells
  • Stimulates enzyme secretion; inhibits gastric secretion + motility
108
Q

Smooth muscle in the GI tract:

  • What is the basal electrical rhythm (BER)?
  • What does it cause?
A
  • The resting membrane potential of the GI tract smooth muscle
  • Constant fluctuation of the membrane potential above and below the threshold potential

HUBS192 EXAM (7 decks)

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